Yet another sizing / option question

Yes, I apologize - yet another softener sizing question. I've read WAAAY too much, and being a sorta-technical person I think I'm getting way too concerned about minor details. It's time to stop analyzing and get this thing done, so....

We have 4 people in our house - 2 adults and two children (ages 5 and 3). One full bath, two 3/4 baths. No other "big" water users (fancy tub / hot tub / jacuzzi) in the house. 3/4" water line.

We're on a municipal water system; testing shows 15 grains of hardness, no iron or manganese. pH = 7.2.

Assuming the conventional 60 gallons per person: 60*15*4=3600 grains per day

A target of 8 days' worth of grains to remove = 28800 grains. That points me to a 1.5 ft^3 softener, sorta on the border between 6 lbs and 8 lbs of salt per lb of resin?

I think (DANGER!) a 1.5 will also handle my SFR requirements, no?

Thinking of Fleck, either 2510SXT or the 7000 head. Our actual water use today isn't quite what the convention shows, so the day override is important.

Do I dare ask if I should get a gravel bed?

Am I headed down the right track here? Anything else I need to consider / measure / check on?

I think you should be fine with a 1.5 as long as your use does not dramatically increase. Either the 2510XT or the 7000 is a fine choice. A gravel bed will service just fine. Sorry that it often gets.......well.....prickly around here but for some reason sizing seems to be as touchy a subject as religion or politics is.

The introduction of a readily available flat bottom distribution system has made this an interesting discussion, but totally wasted as well. We have done extensive teting of the standard distributors with gravel, and the platform style distributors. They are both fine. I prefer the standard softener with a gravel bed because of its lower intial cost, simpler service in the future, and the efficiency is 98% of the platform type. The bottom distributor is the critical part. Many comapnies save a few dollars by supplying a cheap distributor screen in the bottom of the tank. They assume the gravel bed will protect it. I only use the Fleck 40922 or Clack stacked series bottom screens. the Fleck 40922 screen is the best one available, period. IN 5 years we have never had a failure of this screen and it is the only one that we ship our units with, unless a customer has a specific build that they specify a different screen for. It is also the highest rated for flow rate. It has a technical rating of 100 GPM, not that any valve or system can flow that much. It is a spine supported design, the screen area never sees any load other than the media pusing on it. It is similar in design to the D180 screens from years ago but with much higher flow rates and more consistent screen sizes.

For your application the 1.5 Cu. Ft. will be fine. The day overide feature is not as critical as some may make it out to be. It is primarily needed for applications where the water will not be running through the system regularly. We recommend a 14 day override just to minimize the system from getting nasty during times of non use.

The 2510 SXT and the 7000SXT are the best valves available. The 7000 has a much higher flow rate, but this is not critical. it would be like saying my car does 200 MPH, and the 2510 does 150 MPH, really, who cares, they both will greatly exceed anything that you will need.

The 7000SXT is the only valve that is technically rated for outdoor use since it has a NEMA rating. Both valves will do fine outdoors though.
The electronic 2510 meter assembly is its weak point, the part is prone to failure under heavy use,(not common, but far more common than the 7000) and is extremely expensive. The 7000 meter is much less expensive, and rarely fails. The 7000 uses electronic optical positioning, the 2510 uses microswitch positioning. Both are highly reliable. Both systems drive motors are nearly bulletproof, and the piston/seal and spacers are the best in the industry. The 700 bypass is a much newer design and is a true 1-1/4" size, The 7000's main drawback is that it is a huge valve.